Apparatus for optically inspecting object having reflecting surface

ABSTRACT

Apparatus for optically inspecting an object having a reflecting surface includes an irradiating device for emitting illuminating light; a shield member for reflecting the illuminating light to irradiate the object, and a light-receiving device for receiving an image of the object irradiated through the reflection of the illuminating light by the shield member. The shield member covers an extent of a field of vision of the light-receiving device through the reflection of the reflecting surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to apparatus for optically inspecting an objecthaving a reflecting surface to determine whether the object has anydefect such as a flaw, stain and dirt.

2. Prior Art

Examples of objects to be optically inspected include a sheet 100 (FIG.4), such as a polished metal sheet, having a front surface 100a servingas a mirror surface or reflecting surface, a transparent sheet 100 (FIG.5) having a front surface 100a serving as a reflecting surface, and amulti-layer structure 100 (FIG. 6) composed of a plurality of layers,all of the layers being transparent except for the lowermost layer, andthe uppermost layer having a front surface 100a serving as a reflectingsurface. One example of the multi-layer structure is a semi-conductorboard having a plurality of transparent coating layers thereon.

The sheet 100 of FIG. 4 is inspected to determine whether there is anydefect a such as as flaw, stain or dirt on the reflecting surface 100a.The sheet 100 of FIG. 5 is inspected to determine whether there are anydefects b on the reflecting surface 100a and the rear surface and in theinterior. The multi-layer structure 100 of FIG. 6 is inspected todetermine whether there are any defects c on the reflecting surface 100aand at the boundary between the layers and any separation d at theboundary between the layers.

FIG. 7 shows a conventional device for optically inspecting the objects100 which device comprises a probe 110 having a light-receiving portion111 at its front end, an irradiating means 112 in the form of anelectric-light bulb placed in spaced relation to the probe 110, and aconcave mirror 113 to which the irradiation means 112 is secured. Raysof light emitted from the irradiation means 112 are reflected by theconcave mirror 113 and are directed toward an object 100 to beinspected, so that these rays of light are reflected by a reflectingsurface 100a of the object 100 and are fed to the light-receivingportion 111 of the probe 110. Thus, the object 100 is illuminated withhigh brightness to enable any defect (for example, those defectsindicated above by a, b, c and d) to be detected. However, thisconventional device is relatively expensive since the irradiation means112 and the light-receiving portion 111 are separate. In addition, timeand labor are required for properly orienting the irradiation means 112and the light-receiving portion 111. Further, this conventional deviceis rather space-consuming.

To overcome this difficulty, it has been proposed to provide a probe 120(FIG. 8) which is similar in construction to a conventional endoscopeand has a light-receiving portion 121 and an irradiating portion 122 atits front end. The front end of the probe 120 is disposed in opposedrelation to the front surface 100a of the object 100 to irradiate it tocarry out the inspection. With this probe however, an image of theirradiating portion 122 is reflected by the reflecting surface 100a ofthe object 100 and is fed to the light-receiving portion 121, therebycausing halation. This adversely affects the S-N ratio when processingan image signal obtained, and therefore an image of a defect present inthe object can not be accurately detected.

It may be considered to dispose the probe 120 obliquely with respect tothe object 100 to irradiate illuminating light to the reflecting surface100a at an angle so as to prevent an image of the irradiating portion122 from being fed to the light-receiving portion 121. In this case,however, the illuminating light is reflected by the reflecting surface100a to irradiate the background, so that an image of the background isreflected by the reflecting surface 100a and is fed to thelight-receiving portion 121. Therefore, in this case, the S-N ratio isalso affected as described above, and an image of a defect present inthe object can not be accurately detected.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide apparatus foroptically inspecting an object which is relatively inexpensive,space-saving and can accurately detect a defect on the object easily.

According to the present invention, there is provided apparatus foroptically inspecting an object having a reflecting surface whichcomprises irradiating means for emitting illuminating light; shieldmeans for reflecting the illuminating light to irradiate the object, andlight-receiving means for receiving an image of the object irradiatedthrough the reflection of the illuminating light by the shield means,the shield means covering an extent of a field of vision of thelight-receiving means through the reflection of the reflecting surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side-elevational view of a probe provided in accordance withthe present invention;

FIG. 2 is a view similar to FIG. 1 but showing another modified probe;

FIG. 3 is a fragmentary side-elevational view of a further modifiedprobe;

FIGS. 4 to 6 are views of objects to be inspected;

FIGS. 7 and 8 are cross-sectional views of conventional inspectingdevices;

FIGS. 9 to 13 are cross-sectional views of further modified probes;

FIG. 14 is a cross-sectional view of a further modified probe;

FIG. 15 is a cross-sectional view of a further modified probe;

FIG. 16 is a cross-sectional view taken along the line XVI--XVI of FIG.15;

FIG. 17 is a cross-sectional view of a further modified probe;

FIG. 18 is a view as seen in a direction XVIII of FIG. 17; and

FIG. 19 is a cross-sectional view taken along the line XIX--XIX of FIG.17.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

The invention will now be described with reference to the accompanyingdrawings in which like reference numerals denote corresponding parts inseveral view.

A probe 1 shown in FIG. 1 is similar in construction to a rigidinsertion portion of a conventional endoscope and includes an elongatedhollow body. The probe 1 comprises an image-transmitting optical system2 mounted in the body and a bundle 3 of optical fibers mounted in andextending along the body. The optical system 2 includes alight-receiving portion 5 and an objective lens both of which aredisposed at the front end of the probe body. The optical system 2further includes an ocular lens (not shown) disposed at the rear end ofthe probe body and a plurality of lenses interposed between theobjective lens and the ocular lens. The front end of the optical fiberbundle 3 disposed at the front end of the probe body open to serve as anirradiating portion 6, the irradiating portion 6 being disposed in thevicinity of the light-receiving portion 5. The optical axis A of theoptical system 2 is substantially parallel to the axis of the opticalfiber bundle 3.

The rear end of the optical fiber bundle 3 is connected to a lightsource so that light fed from the light source can emit from theirradiating portion 6. The inspection is carried out through the ocularlens with the eye. Alternatively, the image through the ocular lens istaken by either a camera or television camera.

Reference numeral 9 designates a shield plate having a surface 9a whichis a diffusion surface of a white color causing the diffused reflectionof light, the surface 9a having no pattern on it.

The probe 1 can inspect any of the objects 100 shown in FIGS. 4 to 6.

First, the probe 1 is disposed obliquely with respect to an object 100in the form of a sheet to be inspected. The shield plate 9 is alsoinclined with respect to the object 100 and is disposed in mirror imagerelation to the front end of the probe 1 with respect to the surface100a of the object 100. In other words, the shield plate 9 is disposedin such a position that it covers an extent of irradiation of theirradiating portion 6 through the reflection of the surface 100a and anextent of a field of vision of the light-receiving portion 5 through thereflection of the surface 100a.

With this arrangement, illuminating light is applied from theirradiating portion 6 to the object 100, the direction of rays ofilluminating light being oblique with respect to the surface 100a of theobject. The rays of light are reflected by the surface 100a and directedto the shield plate 9 by which the rays of light are subjected todiffused reflection to irradiate the object 100 brightly. The image ofthe object 100 thus irradiated is transmitted via the optical system 2and is taken by a television camera or the like. At this time, theobject is brightly irradiated uniformly, and therefore not only a defecton the surface 100a but also defects in the interior and on the rearsurface can be accurately detected. Where the defect is a separation d(see FIG. 6), it can be detected as an iris.

The direction of irradiation is oblique with respect to the surface 100aof the object 100, so that the image of the irradiation portion 6 ofgreat brightness is reflected toward the shield plate 9 by which it issubjected to diffused reflection and hence is not fed to thelight-receiving portion 5. Therefore, the S-N ratio is not affected whenprocessing the image signal or data, and any defect present in theobject can be accurately detected.

Further, the illuminating light is reflected by the surface 100a of theobject 100 and is intercepted by the shield plate 9, so that it will notirradiate the background. In addition, an image of the background isintercepted by the shield plate 9 and therefore will not be fed to thelight-receiving portion 5 via the surface 100a of the object 100. Inthis respect, also, S-N ratio is not affected.

FIG. 2 shows a modified probe 1a which differs from the probe 1 of FIG.1 in that a shield plate 10 is made of a concave mirror. In thisembodiment, illuminating light from the irradiating portion 6 isreflected by the shield plate 10 back to the surface 100a of the object100 and is further reflected by the surface 100a to be fed to thelight-receiving portion 5. The concave mirror 10 is so positioned thatits focus is disposed at the light-receiving portion 5. The focus may bedisposed near the light-receiving portion 5. Since the image of theirradiating portion 6 is reflected by the concave mirror 10, it is notfed to the light-receiving portion 5 as an appreciable image. Therefore,the irradiating portion 6 will not affect the inspection of a defect inthe object 100. The probe 1a in this embodiment can irradiate the object100 with greater brightness than the probe 1 of FIG. 1, and therefore iswell suited for detecting a defect in the interior of the object and adefect on the rear surface thereof.

The shield plates 9 and 10 may have a light-absorbing surface of a blackcolor so that the rays of light applied thereto can be suitably absorbedthereinto without being reflected by it, in which case a defect on thereflecting surface 100a of the object 100 can only be detected.

Although the irradiating portion is formed by the front end of theoptical fiber bundle in the above embodiments, the irradiating portionmay be formed by an electric-light bulb 7 having a concave mirror 11 andsecured to the front end of a probe 1b as shown in FIG. 3, in which casean optical axis B of the illuminating light emitted from the bulb 7 issubstantially parallel to the optical axis A of an image-transmittingoptical system 4.

FIG. 9 shows a further modified probe 1c similar in construction to arigid insertion portion of a conventional endoscope, the probe 1ccomprising a tubular body 12 having a generally inverted V-shaped notch13 formed in its lower portion adjacent to its front end, the notch 13being defined by front and rear surfaces. An image-transmitting opticalsystem 14 is mounted in the body 12, and a bundle 18 of optical fibersis mounted in and extends along the body 12. The optical system 14comprises a light-receiving window or portion 15 attached to the rearedges of the notch 13 remote from the front end of the body 12, anobjective lens 16 mounted on the light-receiving window 15, a prism 17disposed adjacent to the objective lens 16, and an ocular lens (notshown) disposed at the rear end of the body 12. The optical system 14further includes a plurality of lenses interposed between the objectivelens 16 and the ocular lens. A common optical axis A of thelight-receiving window 15 and objective lens 16 disposed obliquely withrespect to an optical axis B of that portion of the optical system 14extending between the ocular lens and the prism 17 and is directeddownwardly. The optical axes B and A are interconnected via the prism17.

The front end of the optical fiber bundle 18 opens to the rear edges ofthe notch 13 to provide an irradiating portion 18a, the irradiatingportion 18a being disposed adjacent to the light-receiving portion 15.The front end of the optical fiber bundle 18 is cut obliquely and groundso that illuminating light emitted from the irradiating portion 18a canbe directed obliquely upwardly as indicated by arrows in FIG. 9. Therear end of the optical fiber bundle 18 is connected to a light source.

The front surface 19 of the notch 13 serves as a flat reflecting surfaceand is disposed in obliquely opposed relation to the irradiating portion18a. The reflecting surface 19 is a diffusion surface of a white colorcausing the diffused reflection of light.

In operation, the probe body 12 is first disposed substantially parallelto an object 100 to be inspected. The illustrated object 100 is in theform of a sheet, but it may be of a tubular form as indicated at 100' indots and dash lines in FIG. 9. Then, the irradiating portion 18airradiates illuminating light. This illuminating light is not directlyfed to the object 100 but is reflected by the reflecting surface 19 andis subjected to diffused reflection. As a result, the object 100 isirradiated brightly by indirect illumination. The image of the object100 thus irradiated is transmitted via the light-receiving portion 15and the optical system 14 and is taken by a television camera or thelike. At this time, the object 100 is brightly irradiated uniformly, andtherefore not only a defect on the front surface 100a of the object 100but also defects in the interior and on the rear surface can beaccurately detected. Where the defect is a separation d (see FIG. 6), itcan be detected as an iris.

The image of the irradiation portion 18a of great brightness issubjected to diffused reflection by the reflecting surface 19 and henceis not fed to the light-receiving portion 15. Therefore, the S-N ratiois not affected when processing the image signal or data, and any defectpresent in the object can be accurately detected.

Further, the illuminating light is intercepted by the reflecting surface19 and therefore will not irradiate the background, so that an image ofthe background will not be fed to the light-receiving portion 15 via thesurface 100a of the object 100. In this respect, also, the S-N ratio isnot affected. The reflecting surface 19 is disposed in such a positionthat it covers an extent of irradiation of the irradiating portion 18aand an extent of a field of vision of the light-receiving portion 15achieved by the reflection of the surface 100a.

FIG. 10 shows a further modified probe 1d which differs from the probe1c of FIG. 9 in that a reflection surface 20 is formed by a concavemirror. In this embodiment, illuminating light emitted from theirradiating portion 18a is reflected by the reflecting surface 20 andfed to the surface 100a of the object 100 by which the illuminatinglight is reflected toward the light-receiving portion 15. The focus ofthe reflecting surface 20 is disposed at the objective lens 16. Thefocus may be disposed near the objective lens 16. The image of theirradiating portion 18a is reflected by the reflecting surface 20 in theform of a concave mirror, and therefore is not fed to thelight-receiving portion 15 as an appreciable image. The probe 1d in thisembodiment can irradiate the object 100 with great brightness, andtherefore is well suited for detecting a defect in the interior of theobject and a defect on the rear surface thereof.

FIG. 11 shows a further modified probe 1e which differs from the probe1c of FIG. 9 mainly in that a cross-sectionally circular bundle 18 ofoptical fibers is mounted within a tubular body 12 and extendstherealong and in that a shield plate 19 is secured to the outer surfaceof the tubular body 12 at a front end thereof. The front end of thetubular body 12 is slightly bent downwardly and is cut obliquely, andthe optical fiber bundle 18 fitted on the inner surface of the tubularbody 12 is also bent downwardly at its front end. An inner tube 23 isreceived within the optical fiber bundle 18 of a circular cross-section,and the image-transmitting optical system 14 is mounted within the innertube 23.

The shield plate 19 is of a generally V-shape and has a front halfdisposed substantially parallel to the common optical axis A of thelight-receiving window 15 and objective lens 16, the front half of theshield plate 19 having an inner flat surface 19a which is a diffusionsurface of a white color causing the diffused reflection of light.

In operation, the probe body 12 is first disposed substantially parallelto an object 100 to be inspected. Then, the irradiating portion 18afeeds illuminating light to the object 100, the direction of feed of theilluminating light being inclined with respect to the surface 100a ofthe object 100. The illuminating light is reflected by the surface 100aand is fed to the surface 19a of the shield plate 19 by which theilluminating light is diffusedly reflected to irradiate the object 100brightly. An image of the object 100 thus irradiated is fed via thelight-receiving portion 15 and the optical system 14 to the ocular lensat the rear end of the tubular body and is taken by a television cameraor the like. At this time, the object 100 is brightly irradiateduniformly, and therefore not only a defect on the surface 100a but alsodefects in the interior and on the rear surface can be accuratelydetected. Where the defect is a separation d (see FIG. 6), it can bedetected as an iris.

The direction of irradiation is oblique with respect to the surface 100aof the object 100, so that the image of the irradiation portion 18a ofgreat brightness is reflected toward the shield plate 19 by which it issubjected to diffused reflection and hence is not fed to thelight-receiving portion 15. Therefore, the S-N ratio is not affectedwhen processing the image signal or data, and any defect present in theobject can be accurately detected.

Further, the illuminating light is reflected by the surface 100a of theobject 100 and is intercepted by the shield plate 19, so that it willnot irradiate the background. In addition, an image of the background isintercepted by the shield plate 19 and therefore will not be fed to thelight-receiving portion 15 via the surface 100a of the object 100. Inthis respect, also, the S-N ratio is not affected. Thus, the shieldplate 19 covers an extent of irradiation of the irradiating portion 18aby the reflection of the surface 100a and an extent of a field of visionof the light-receiving portion 15 achieved by the reflection of thesurface 100a.

FIG. 12 is a further modified probe 1f which differs from the probe 1eof FIG. 11 in that a tubular body 12 is straight with the optical axis Aaligned with the optical axis B and in that a shield plate 19 is securedto the outer surface of the body 12 in parallel relation to the axis ofthe body 12. An optical fiber bundle 18 is also straight, and anauxiliary tube 21 is interposed between the body 12 and the opticalfiber bundle 18, and the tubular body 12 is rotatable relative to theauxiliary tube 21 and movable therealong. With this construction, theposition of the shield plate 19 is suitably adjusted to achieve theoptimum irradiation effect. In operation, the probe body 12 is disposedobliquely with respect to the object 100, so that the direction of feedof the illuminating light from the irradiating portion 18a is alsooblique relative to the surface 100a of the object 100.

FIG. 13 shows a further modified probe 1g which differs from the probe1f of FIG. 12 in that the auxiliary tube 21 is omitted and in that ashield plate 19 is secured to the outer surface of the tubular body 12in oblique relation to the axis of the body 12. In operation, the probebody 12 is disposed obliquely with respect to the object 100, and theshield plate 19 disposed parallel to the object 100. If the shield plate19 is long, the inspection can also be carried out with the probe 1gdisposed remote from the object 100.

FIG. 14 shows a further modified probe 1h in which a bundle 18 ofoptical fibers and an image-transmitting optical system 14 are mountedwithin a body 12 in non-coaxial relation. A shaft 22 mounted in the body12 so as to be rotatable relative thereto and movable along an axisthereof, a front end of the shaft 22 extending beyond the front end ofthe body. A shield plate (not shown) is secured to the front end of theshaft 22. With this construction, the position of the shield plate canbe adjusted.

FIGS. 15 and 16 show a further modified probe 1i in which animage-transmitting optical system 14 and a bundle 18 of optical fibersare mounted within a tubular body 12 in non-coaxial relation. A tubularbody 12 is open at its front end and has an integral shield plate 19formed at its front end and slanting downwardly in a direction away froma light-receiving portion 15. A front end of an optical fiber bundle 18serving as an irradiating portion 18a is cut obliquely and faces theshield plate 19, so that illuminating light from the irradiating portion18a is directed obliquely downwardly toward an object 100 as shown inFIG. 15. A common axis of a light-receiving portion 15 and objectivelens 16 is also disposed obliquely with respect to the object 100.

FIGS. 17 to 19 show a further modified probe 1j in which a pair ofoptical fiber bundles 18 are secured to the outer surface of a tubularbody 12 in diametrically opposed relation. An inner tube 23 is receivedin the tubular body 12, and an image-transmitting optical system 14 isreceived in the inner tube 23. The tubular body 12 is open at its frontend and has an integral shield plate 19 formed at its front end andslanting downwardly in a direction away from a light-receiving portion15. The tubular body 12 is rotatable relative to the inner tube 23 andis movable therealong so that the position of the shield plate 19 can beadjusted. A common axis of a light-receiving portion 15 and objectivelens 16 is also disposed obliquely with respect to the object 100. Thefront ends of the optical fiber bundles 18 are oriented inwardly anddownwardly, and illuminating light from each of irradiating portions 18ais fed to an object 100 in the vicinity of a point where the axis Aintersects the object 100.

While the probes according to the invention have been specifically shownand described herein, the invention itself is not to be restricted bythe exact showing of the drawings or the description thereof. Forexample, in the above embodiments, although the light-receiving portionand the image-transmitting optical system are similar in construction toan insertion portion of a conventional endoscope, they may be replacedby a photosensor and an image sensor.

What is claimed is:
 1. An apparatus for optically inspecting defects onand/or within an object having a reflecting surface comprising:(a)irradiating means for emitting illuminating light; (b) shield meanshaving a reflecting surface for reflecting the illuminating light toirradiate the object, and (c) an image-transmitting optical systemincluding light-receiving means for receiving an image of the objectirradiated through the reflection of the illuminating light by saidshield means, and means for optically transmitting the image of theobject received by said light-receiving means, and said shield meanscovering an extent of a field of vision of said light-receiving meansthrough the reflection of the reflecting surface, in which said shieldmeans comprises a concave mirror, the focus of said concave mirror beingdisposed at said light-receiving means, and in which said irradiatingmeans is directed toward the reflection surface of the object, saidshield means being disposed in opposed relation to said irradiatingmeans in such a manner that the illuminating light is fed to said shieldmeans through the reflection by the reflection surface of the object. 2.Apparatus according to claim 1, further comprising an elongated body,said irradiating means and said light-receiving means being mounted onone end of said body.
 3. An apparatus according to claim 1, furthercomprising an elongated body, an image-transmitting optical system beingmounted in said elongated body and including a bundle of optical fibersextending along said elongated body, said bundle of optical fibershaving one end thereof disposed at one end of said elongated body toform said irradiating means.
 4. An apparatus according to claim 3,wherein said light-receiving means is disposed at said one end of saidelongated body, and said image-transmitting optical system has anoptical axis extending substantially parallel to an axis of said bundleof optical fibers.